Carpal tunnel syndrome results from compression of the median nerve within the carpal tunnel of the hand. It occurs most often in people between 30 and 60 years old and is several times more frequent in women than in men. Any condition that crowds or reduces the size of the carpal tunnel may initiate the symptoms. If there are mild symptoms present, injection of hydrocortisone into the carpal tunnel may afford relief. When symptoms are persistent and progressive, however, division of the deep transverse carpal ligament is recommended.
In the 1950's, a procedure was developed for releasing the carpal tunnel ligament by pushing a closed blade. The procedure was rapidly discredited because of its inaccuracy and consequent failure rate. The original blade assembly resembled a meniscatome blade, but because the pathway of the blade was not directly controlled, it was possible for the surgeon to aim incorrectly and thereby sever nerves, arteries, or tendon structures. This was a truly blind procedure without guidance from additional devices or visualization.
Shortly after that, surgeons began using an open surgical technique, which is still the prevalent surgical treatment. Briefly, various curved or zig-zag incisions are made from a point ulnar to and paralleling the thenar crease to approximately the flexor crease of the wrist. The skin and subcutaneous tissue are incised, and the transverse carpal ligament then divided. The incision is closed and the wound drained as needed.
Following open surgical release, swelling at the base of the palm superficial to the carpal tunnel tends to persist for 12 to 16 weeks. During this time, the patient often experiences aching pain in the thenat or hypothenar eminences. Gripping activity aggravates the pain and may cause shooting sensations into the forearm. Resolution of the swelling is usually accompanied by relief of the pain.
Further results from open surgical release often include a tender scar, a hospital stay, and sometimes an incomplete release of the transverse carpal ligament.
A recent surgical procedure involves the use of an endoscope. The concept of the endoscopic technique is to permit constant visualization during the surgery. Briefly, the procedure requires a surgeon and an assistant. Approximate landmarks on the hand establish entry and exit portals which are marked. Incision at the proximal entry portal on the volar surface of the wrist is made using appropriate surgical incision tools. A slotted cannula assembly is guided into the entry portal incision space. The wrist and fingers of the hand must then be bent in full hyperextension. As a consequence, this procedure is not available to patients with stiff wrists which are unable to be hyperextended. An obturator fitted in the cannula advances against the transverse carpal ligament, using it as a ceiling. When the tip of the obturator reaches the pre-marked exit portal, a small incision is made and the slotted cannula assembly is pushed through. The obturator is removed from the cannula. A video endoscope is then inserted into the slotted cannula. The instrument is used to visualize the entire carpal ligament. If difficulty in accessing the ligament is experienced, the video endoscope must be removed, the obturator reinserted, the cannula assembly removed, and the placement procedure started again. When the surgeon is confident of understanding the carpal ligament, the video endoscope is moved out of the way with respect to the slotted cannula and various knife tools are inserted with the knife extending upwardly from the slot. After some cutting is done, the endoscope may be moved into place to view the cut. In this way, eventually the ligament is completely divided. Following removal of the video endoscope, the obturator is reinserred and the assembly removed with the wound then being sutured and given appropriate care.
The endoscopic release procedure seems to result in a less tender scar and possibly a faster recovery, perhaps 2 to 4 weeks. The costs of the procedure, however, are higher. There is a hospital stay. The procedure requires wrist hyperextension which is not possible with some patients. Although the visualization concept is attractive, there is considerable question whether anything useful is really seen.
In a recent study, with patients not receiving worker's compensation, it was verified that endoscopic patients return to work in about one-third the time of those having open surgical release. The endoscopic procedure is presently not recommended, however, since the present procedure does not address the possibility of cutting nerves and vessels over the ligament and with some patients there has been nerve injury.
Thus, open surgical release procedure remains the most prevalent treatment for carpal tunnel syndrome having more advanced symptoms so that division of the transverse carpal ligament is indicated. Some of the more positive results, however, of the endoscopic release technique, such as, less tender scar and faster recovery time, show that improvements are possible. This gives impetus to development of the present invention. The present invention requires appropriate testing, but is expected to provide a more reliable and safer, much quicker and less expensive surgical technique than the endoscopic technique and should result in less pain and tenderness and faster recovery.